when will the slush disappear - Newbie Question

[67red]

Someone help me understand the science here.  Went out yesterday - there was 6" of snow on top, then 2" of Ice/frozen snow, then 6" of slush/water, then 8" of ice.  When I shoveled off and drilled thru I had 6" of water on top of my hole.

So I understand the snow is insulating the area below and therefore the slush isn't refreezing, but since the regular ice is below the slush - won't the 8" of ice start to melt?  I was also told that all the weight on top of the ice is causing it to sink just a bit, hence the water on top of the ice once I drill a hole.

It has been single digit temperatures for a few days - will the stuff on top of the ice ever freeze up?  or do we need a melt and then a freeze?

It was pretty bad trudging thru that stuff yesterday

Thanks in advance

[oletimer]

We need a short warm up, maybe even a little rain. Would settle the snow and slush, then another arctic blast to refreeze....

[Nick94]

w/ temps like this, it may freeze, but a melt and then more cold would be much better.  

now a answer that may get a little confusing (sorry if it does)
water can be at 32 degrees F and not freeze, the phase change from liquid to solid or reverse requires a lot of energy to enter/leave the substance (in this case water) but the temperature at the phase change does not change.  just to give you an idea, the energy required to melt/freeze water (called heat of fusion) requires 333550 J/kg, about 320 BTU/kg (1 kg=2.2 lbs).  and since 1 gram of water has a volume  of 1 ml or 1 cm by 1cm by 1cm, 1kg of water has a volume of 1000 ml or 1000 cubic centimeters or 61.0237 cubic inches (that is a cube about 3.9 inches by 3.9 inches by 3.9 inches). and there are literally millions of liters of water to freeze.  that requires a huge amount of energy to leave the water, but the snow prevents it from doing so too quickly.  and so it takes a long time (and sometimes, depending on temps, it can be slushy all winter).  

[shark]

w/ temps like this, it may freeze, but a melt and then more cold would be much better.  

now a answer that may get  a little confusing (sorry if it does)
water can be at 32 degrees F and not freeze, the phase change from liquid to solid or reverse requires a lot of energy to enter/leave the substance (in this case water) but the temperature at the phase change does not change.  just to give you an idea, the energy required to melt/freeze water (called heat of fusion) requires 333550 J/kg, about 320 BTU/kg (1 kg=2.2 lbs).  and since 1 gram of water has a volume  of 1 ml or 1 cm by 1cm by 1cm, 1kg of water has a volume of 1000 ml or 1000 cubic centimeters or 61.0237 cubic inches (that is a cube about 3.9 inches by 3.9 inches by 3.9 inches). and there are literally millions of liters of water to freeze.  that requires a huge amount of energy to leave the water, but the snow prevents it from doing so too quickly.  and so it takes a long time (and sometimes, depending on temps, it can be slushy all winter).  

 


   What Nick said         ,          I have go take a nap now ,that took a lot out of me.............

[67red]

Thank you - got what I asked for and I now understand the science part.  A bit more in depth then what I had in mind - impressive none the less.

So is the Ice that is between the slush and the body of water not in danger of melting because it already displaced the energy, and the cold water surrounding it is keeping it frozen?

 

[filetandrelease]

it can freeze all it wants but the little O isn't going to make ice unless the snow gets saturated

[SNAGGER]

w/ temps like this, it may freeze, but a melt and then more cold would be much better.  

now a answer that may get a little confusing (sorry if it does)
water can be at 32 degrees F and not freeze, the phase change from liquid to solid or reverse requires a lot of energy to enter/leave the substance (in this case water) but the temperature at the phase change does not change.  just to give you an idea, the energy required to melt/freeze water (called heat of fusion) requires 333550 J/kg, about 320 BTU/kg (1 kg=2.2 lbs).  and since 1 gram of water has a volume  of 1 ml or 1 cm by 1cm by 1cm, 1kg of water has a volume of 1000 ml or 1000 cubic centimeters or 61.0237 cubic inches (that is a cube about 3.9 inches by 3.9 inches by 3.9 inches). and there are literally millions of liters of water to freeze.  that requires a huge amount of energy to leave the water, but the snow prevents it from doing so too quickly.  and so it takes a long time (and sometimes, depending on temps, it can be slushy all winter).  

  What's the freezing point for saltwater?   

[icedpapermouth]

 


   What Nick said         ,          I have go take a nap now ,that took a lot out of me.............

 

[Nick94]

  What's the freezing point for saltwater?   

  What's the freezing point for saltwater?   

you had to ask....

well the freezing point of a fluid is dependent on a few things; a) the fluid itself and it's normal freezing point; b) the molality of the solution; and c) the type of material dissolved in it

the Formula for freezing point depression is ΔT=imK
ΔT is the change in freezing temperature
i is the van't Hoff factor of a solute
m is the molality of a solution
K is the freezing point depression molal constant, which for water is 1.86 (degrees C * kg)/m

Part A)
pure water has a freezing point of 0 degrees C or 32 degrees F and disolves most salts (salt in the chemistry sense, a metal and non-metal like SodiumChloride, other ions that would be found but i am not sure of the pairings would be Ca+2, Mg+2, Nitrates, Nitrites, Phosphates, etc)

Part B
molality is a way to measure the concentration of a substance (the solute) in a fluid (the solvent).  molality, represented by the lowercase letter 'm' is equal to moles of solute divided by kilograms of solution (moles of solute)/(kg of solution). so if you have a 2 m solution of saltwater, you would have 2 moles of sodium chloride (116.88 grams) dissolved in 1 kg of pure water.

a mole, Avogadro's number, is a sample of the substance containing 6.022x10^23 molecules of the substance (the exact number is unknown but is somewhere around  602,214,141,070,409,084,099,072).  1 mole of a substance has the same mass in grams as the atomic mass on the periodic table (1 mole of sodium has a mass of 22.99 grams)

Part C
now come's van't Hoff factor.
The van't Hoff factor, simply, is the number of ions a solute forms when it is dissolved. For example, sodium chloride dissolves to form 2 ions, sodium ions and chlorine ions so the theoretical van't Hoffs factor is 2.  however, the actual van't Hoffs factor is always slightly less then theoretical because when in solution, particles exhibit random motion, colliding into the sides and different particles.  and therefore, just by freak occurrence, there are always some ions bonded to form the normal molecule, so there are not quite as many ions dissolved, hence the 1.9. as a solution becomes more concentrated, the van't Hoff's number gets farther and farther from theoretical (for example, sodium chloride, at 0.1 m has a i of 1.87, at 0.01m i=1.94, at 0.001m i=1.97).  however, not all materials dissolve and ionize/dissasociate in water.  sucrose (sugar) does not form ions, therefore the theoretical and actual van't Hoffs factor are the same, 1.

i=moles of ions divided by the moles of solute=(moles of ions)/(moles of solute)

so, if you have, say 10 grams of salt dissolved in 2 kg of water (2 liters), it would freeze at:
ΔT=imK
i=2 (theoreticlaly)
m=   (10 grams=.171116 moles)  0.171116 moles/2 kg=0.0855578m
K=1.86 Ckg/m

ΔT=2*0.085578m*1.86Ckj/m
ΔT=.318 C

so the freezing point would be -0.3.18 degrees C.


most seawater has a freezing point of -2 C or about 29 F

[darkdoug]

good god, Snagger.....does this stuff run thru your mind in between fish? Thats some impressive science !

[SchrnLker]

you had to ask....

well the freezing point of a fluid is dependent on a few things; a) the fluid itself and it's normal freezing point; b) the molality of the solution; and c) the type of material dissolved in it

the Formula for freezing point depression is ΔT=imK
ΔT is the change in freezing temperature
i is the van't Hoff factor of a solute
m is the molality of a solution
K is the freezing point depression molal constant, which for water is 1.86 (degrees C * kg)/m

Part A)
pure water has a freezing point of 0 degrees C or 32 degrees F and disolves most salts (salt in the chemistry sense, a metal and non-metal like SodiumChloride, other ions that would be found but i am not sure of the pairings would be Ca+2, Mg+2, Nitrates, Nitrites, Phosphates, etc)

Part B
molality is a way to measure the concentration of a substance (the solute) in a fluid (the solvent).  molality, represented by the lowercase letter 'm' is equal to moles of solute divided by kilograms of solution (moles of solute)/(kg of solution). so if you have a 2 m solution of saltwater, you would have 2 moles of sodium chloride (116.88 grams) dissolved in 1 kg of pure water.

a mole, Avogadro's number, is a sample of the substance containing 6.022x10^23 molecules of the substance (the exact number is unknown but is somewhere around  602,214,141,070,409,084,099,072).  1 mole of a substance has the same mass in grams as the atomic mass on the periodic table (1 mole of sodium has a mass of 22.99 grams)

Part C
now come's van't Hoff factor.
The van't Hoff factor, simply, is the number of ions a solute forms when it is dissolved. For example, sodium chloride dissolves to form 2 ions, sodium ions and chlorine ions so the theoretical van't Hoffs factor is 2.  however, the actual van't Hoffs factor is always slightly less then theoretical because when in solution, particles exhibit random motion, colliding into the sides and different particles.  and therefore, just by freak occurrence, there are always some ions bonded to form the normal molecule, so there are not quite as many ions dissolved, hence the 1.9. as a solution becomes more concentrated, the van't Hoff's number gets farther and farther from theoretical (for example, sodium chloride, at 0.1 m has a i of 1.87, at 0.01m i=1.94, at 0.001m i=1.97).  however, not all materials dissolve and ionize/dissasociate in water.  sucrose (sugar) does not form ions, therefore the theoretical and actual van't Hoffs factor are the same, 1.

i=moles of ions divided by the moles of solute=(moles of ions)/(moles of solute)

so, if you have, say 10 grams of salt dissolved in 2 kg of water (2 liters), it would freeze at:
ΔT=imK
i=2 (theoreticlaly)
m=   (10 grams=.171116 moles)  0.171116 moles/2 kg=0.0855578m
K=1.86 Ckg/m

ΔT=2*0.085578m*1.86Ckj/m
ΔT=.318 C

so the freezing point would be -0.3.18 degrees C.


most seawater has a freezing point of -2 C or about 29 F

My hair hurts

[pooley]

  What's the freezing point for saltwater?   

28 degrees.

better guys? LOL!

oh, and after a week or more, ice from saltwater turns fresh if it's no longer in contact with the saltwater.

[NNYIceangler]

Not nearly as technical an answer as others- but you can help the situation, if you fish the same area.  The more holes you pop, the more water comes up, the more snow absorbs the water.  That snow/slush will turn to snow ice and will allow for easier building of black ice underneath. 

I have always said this...when an are gets hit hard one weekend, all the water seeps up and turns to slush, once it gets cold it seems to harden up nicely.  I am hoping for this on my waters because I dont see a warm up anytime in the near future.